Now we know why people have been dosing themselves with the animal tranquillizer ketamine for years. Scientists have learned that ketamine, known to the experimental among you as Special K, is a powerful, fast-acting antidepressant.

Psychologists have known for a while that ketamine seems to instantly cure severe depression, and is especially helpful for suicidal people. One dose of ketamine can ease depression for weeks.

But scientists weren't sure why. University of Texas Southwestern Medical Center researcher Lisa Monteggia and her colleagues decided to find out. They gave depressed mice doses of ketamine, observed behavior changes, and examined exactly what happened in the rodents' brains when the drug kicked in. What they discovered was that ketamine is essentially a fast-acting version of traditional antidepressants like Prozac, a selective serotonin re-uptake inhibitor (SSRI). SSRIs can take weeks to have an effect, however, while ketamine is almost instantaneous.

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What these ketamine experiments reveal is a set of neurochemical pathways in the brain that, when manipulated, can ease depression very quickly.

A release about the study in Nature offers a technical explanation:

Lisa Monteggia and colleagues studied how ketamine and other similar NMDA receptor antagonists function in a mouse model. They found that blocking NMDA receptors with ketamine leads to the deactivation of a factor involved in protein synthesis, eEF2 kinase, which in turn results in the promotion of BDNF synthesis. The authors found that by inhibiting eEF2 kinase, they could induce a fast-acting behavioural change similar to that caused by traditional antidepressants. As ketamine can have significant side effects, this work raises other potential points of interest in the pathway that could be targeted.

Though ketamine's many side-effects make it a non-ideal solution for depression, Monteggia's experiments have shown researchers that there are new ways to change neurological activity in the brain to get results that are better than those of traditional antidepressants. Our moods are not set in stone, and are in fact very easily shifted with the proper chemical intervention.

It's possible that all those raver kids taking Special K in the 1990s weren't just in it for the high. The drug may have been easing their depression too.